Mozilla releases 64-bit Firefox Developer Edition for Windows

Martin Brinkmann
Feb 28, 2015
Updated • Feb 28, 2015

Windows users who wanted to run a 64-bit version of Firefox in the past were limited to the Nightly Channel up until now as it was the only channel that offered 32-bit and 64-bit versions of Firefox on Windows.

All other channels, Stable, Beta and Developer Edition, were not offered as a 64-bit version for the Windows operating system.

The situation is different for Mac and Linux versions of Firefox as 64-bit versions for both systems have been made available for some time now by Mozilla.

Firefox users who wanted to run 64-bit versions of Firefox on Windows had to either use the Nightly version or switch to forks of the browser such as Pale Moon or Waterfox that are offered as 64-bit versions.

Mozilla added 64-bit support on Windows to the Developer Edition of Firefox recently (formerly know as Aurora).

When you open the download page on the Mozilla website you find Windows 64-bit versions listed for all localized versions on the page.

The move marks the beginning of the final phase of adding full 64-bit support to all versions of Firefox.Soon, first 64-bit beta builds will become available (starting with Firefox 37 Beta 2).

This means that 64-bit builds will be generated next to 32-bit builds. These 64-bit builds won't be listed on the Beta download page though for the foreseeable future. According to Mozilla's Robert Kaiser, this won't happen before Beta builds are moved to version 38 at the earliest (in five weeks).

No word yet on when stable versions of Firefox will be made available officially as 64-bit versions.

So what are the core differences between 32-bit and 64-bit versions of Firefox on Windows? There are a few and not all are positive.

On the positive side, you get better speed, security and stability even though this varies a lot depending on how you are using the browser. The 64-bit version of Google's browser Chrome for example offers improvements in graphics and media benchmarks, is twice as stable and defends better against certain attack forms.

It is likely that similar benefits come with 64-bit versions of Firefox.

Mozilla too gives reasons why 64-bit is important. Web applications and games are becoming complex and will benefit from 64-bit both performance wise but also memory wise.

The release of a 64-bit version may help Mozilla stay competitive (most competing browsers are offering 64-bit versions on Windows already).

Last but not least, there are rumors that Microsoft may ship Windows 10 as a 64-bit version only.

The downsides to running a 64-bit version of Firefox are that some plugins won't be supported since you can only install 64-bit versions of plugins, and that the memory overhead of the browser is higher.

It is unclear at this point in time if Firefox 38 will be the first version of the browser that supports 64-bit officially on Windows on all channels. Even if it won't be the first version, it is clear that a 64-bit version of Windows will land in one of the next stable updates. (via Sören)

How to find out if you are running a 64-bit version of Firefox

firefox 64-bit

It is relatively easy to find out if you are running a 64-bit version of Firefox on Windows.

  • Make sure Firefox is running.
  • Use Ctrl-Shift-Esc to open the Task Manager.
  • If you see firefox.exe listed there, it is a 64-bit version.
  • If you see firefox.exe *32 there, it is a 32-bit version.
Mozilla releases 64-bit Firefox Developer Edition for Windows
Article Name
Mozilla releases 64-bit Firefox Developer Edition for Windows
Mozilla has made available 64-bit builds of Firefox's Developer Edition officially for the Windows operating system.

Tutorials & Tips

Previous Post: «
Next Post: «


  1. nero said on March 6, 2015 at 2:59 pm

    My only issue with x64 is that there’s no Hangouts plug-in.

  2. Å ime Vidas said on March 3, 2015 at 4:03 am

    Btw, on Windows 8.1, Firefox’s process is listed as “Firefox (32 bit)” in the Task Manager.

  3. Torro said on March 2, 2015 at 5:41 pm

    I am looking forward to this and hope our favorite add-ons are quickly modifued for 64bit use.

  4. Neal said on March 1, 2015 at 7:07 pm

    Extremely disappointed, it was planned for Firefox 37 and now they say it might not be even in Firefox 38. The next Firefox ESR version will be based on Firefox 38. I was hoping 64 bit Firefox would land before the new ESR came out. E10 whenever it releases will be extremely disruptive, I was hoping to have the option to fall back to a 64 bit Firefox ESR version, but if it 64 bit doesn’t land in Firefox 38, then yeah…..

  5. Ahmed said on March 1, 2015 at 3:43 am

    I am currently running a 64-bit version of Firefox by pcxFirefox. The performance is amazing. I was previously running Firefox 32-bit version 26.0 and getting a Peacekeeper score of about 2700. After upgrading to pcxFirefox version 35.0.1, my Peacekeeper score is about 5900. That is more than twice the performance. Also, the browser is more stable, responsive, and a lot fewer crashes. This is probably a combination of both using a later version of Firefox and switching to 64-bit.

    My start up time is about 4-5 seconds which is not bad considering that I am running with about a hundred addons. I provide a link below to pcxFirefox.

  6. Karl said on February 28, 2015 at 10:09 pm

    Already running 64 bit Firefox in Mint Linux 17 64 bit LTS! :)

  7. Guest said on February 28, 2015 at 9:43 pm

    “Last but not least, there are rumors that Microsoft may ship Windows 10 as a 64-bit version only.”

    This would be wonderful. 32-bit Windows should have gone out the Window back with the release of Windows 7.

  8. LegoActionFigure said on February 28, 2015 at 8:10 pm

    What doesn’t make sense is the whole idea why companies are slow to release 64b versions when Windows has been available as a 64b version since XP. A good majority of the programs released even today are only 32b programs. Even those of us who built our machines for gaming purposes only to find out the game only comes in a 32b version and even worse it won’t work with multi-cores as with most programs.

    Multi-core architecture has been available for some time now and those of us who have purchased new machines within the last 10 years, chances are it is a minimum dual core machine on a 64b version of Windows. And since companies are so slow to adapt to 64b architecture other companies are making leaps and bounds and no longer limited to using CPU cores. Next step, opening the throttle on GPU cores (nVidia CUDA or Intel HD 3rd Generation), which is even faster than relying on the CPU and it’s limited bottle necks.

    The day I replaced all my browsers with 64b versions (Nightly 39.0a1 (2015-02-28) & Chrome 42.0.2311.11 dev-m (64-bit)) is the day I found freedom. Simply opening my browsers with all my customizations and extension used to take 10-15 seconds on average. So while the rest of you click open your browsers and surf, I’m looking at a blank white screen while all my extensions are loaded in. Since running 64b version, this has drastically speed up response time to mere seconds (1-3) instead of what seemed like an awful amount of time to wait to open anything. Now if only browsers used multi-cores 100% of the time.

  9. Boris said on February 28, 2015 at 5:53 pm

    I do not care about memory overhead high (it is high right now) as long as browser is much more responsive. Also have zero problems with plugins as I use only two flash/silverlight as they both have 64bit versions. I will be switching as fast as they release stable version.

  10. Peter (NL) said on February 28, 2015 at 3:15 pm

    Thank you for this article. Very nice to learn that developments are going on towards a Firefox 64-bit browser. I look forward to the actual memory usage (reduction of mem usage) when it is released as the final stable version.

    Jonathan Nightingale will stop as Engineering Lead at Mozilla, so it is interesting to see what will happen in their plans and strategy.

    1. Martin Brinkmann said on February 28, 2015 at 3:20 pm

      I think it is about time that Mozilla releases a 64-bit version of Firefox Stable.

      1. Sukhen said on February 28, 2015 at 4:16 pm

        Don’t know when they will. Anyway, No issues so far with CyberFox x64.

  11. dave said on February 28, 2015 at 12:22 pm

    windows 10 will not be 64bit only, microsoft have already confirmed this, please fix the article.

    1. Martin Brinkmann said on February 28, 2015 at 12:30 pm

      Dave thanks, corrected.

      1. PhoneyVirus said on March 4, 2015 at 3:37 am

        Bad enough we lost support for older applications because of 64-bit, 32-bit will always come with 64-bit versions, that’s of course we don’t move to 128-bit, then 32-bit would get dropped in favor of 64-bit.

  12. larry said on February 28, 2015 at 10:55 am

    Martin, I’ve disabled Adblock Edge, noscript (whitelisted) but show no ads and IE11 no difference. What would I have to do? Cyberfox is my main browser.

    1. Martin Brinkmann said on February 28, 2015 at 12:12 pm

      Hm, it is difficult to find out why that is the case. Maybe something else is blocking ads system wide, a hosts file maybe?

      1. Larry said on February 28, 2015 at 2:32 pm

        I’ve reverted back my hosts file to a default settings nonetheless ads no show. I’ve Noscript whitelised all on ghacks and now shows ads. Relief!

      2. Martin Brinkmann said on February 28, 2015 at 3:17 pm

        Thanks so much Larry!

  13. Saad said on February 28, 2015 at 9:50 am

    Please see this page:

    the first New. it is not in beta !

    1. Emilio said on February 28, 2015 at 9:31 pm

      It is for users at random and must be enabled telemetry.

    2. Martin Brinkmann said on February 28, 2015 at 9:56 am

      Saad it seems that it is integrated but only a “random subset of users” gets experiments each day that they can rate.

  14. Saad said on February 28, 2015 at 9:47 am

    Aurora(Developer Ed) Win64 is not much new. now users waiting for Beta win64 in v37.

Leave a Reply

Check the box to consent to your data being stored in line with the guidelines set out in our privacy policy

We love comments and welcome thoughtful and civilized discussion. Rudeness and personal attacks will not be tolerated. Please stay on-topic.
Please note that your comment may not appear immediately after you post it.